But wait, the endcaps don't need to be warm for humans. In fact, we
would like them to be quite cold at the center, around 40C to 50C colder
than the rim, in order to give the air a decent lapse rate and keep the
atmosphere stabile. ....
Perhaps we do want the endcaps cold, but colder air higher up does
not keep the atmosphere stable.
On the contrary cold air higher up makes for unstable air, with
consequences such as thunderstorms. Warmer air over cooler air is
called an `inversion'. It is more stable than the reverse.
Inversions over cities are infamous for trapping pollutants in a
relatively small volume rather than diluting them through a large
volume.
(By the way, the meaning of the words `warm' and `cold' is not
absolute, but relative to the neutral temperature at the relevant
altitude. `Warmer air' may have a lower absolute temperature than air
at the surface; the atmosphere is stable so long as the `warmer' air
is warmer than the air at the surface would be if raised to the higher
altitude.)
Instability occurs when a parcel of air that is low down rises a
little bit (say a fraction of a centimeter), and even though that
parcel cools as it rises, since its pressure drops, that parcel does
not cool to the temperature of the surrounding air, so that parcel of
air continues to rise. The key is that the drop in temperature of the
parcel of air from the surface be less than the drop in temperature of
the column of air, so that a rising parcel is relatively warmer than
its surroundings.
Meteorologists use `skew-t' sounding diagrams to show what happens.
See, for example:
http://orbit-net.nesdis.noaa.gov/goes/soundings/skewt/html/skewtinf.html
Soundings (Skew-T) explanation
http://www.rap.ucar.edu/weather/upper/alb.gif
Albany, NY (KALB) sounding, evidentally from radiosonde
http://orbit-net.nesdis.noaa.gov/goes/soundings/skewt/html/alb.html
Albany, NY (KALB) sounding from GOES with parameter info
--
Robert J. Chassell Rattlesnake Enterprises
http://www.rattlesnake.com GnuPG Key ID: 004B4AC8
http://www.teak.cc [EMAIL PROTECTED]
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